Field of the Invention
The present invention relates to a polyacetal resin composition and to a sulfur-containing fuel contact body provided by a molded article of this polyacetal resin composition, and to a method of increasing acid resistance with respect to an acidic component using a molded article of this polyacetal resin composition.
Description of the Related Art
Polyacetal resins have excellent chemical resistance, thus molded articles having a polyacetal resin as a raw material have been widely used for automobile components. For example, they have been used for large components which directly contact fuel oil such as fuel delivery units and the like, represented by fuel pump modules and the like.
In recent years, in order to respond to environmental regulations of various countries, sulfur reduction of fuels has progressed. However, desulfurization equipment can be highly costly, therefore, in some countries, high sulfur-containing fuel is still being distributed. These high sulfur-containing fuels, compared to low sulfur-containing fuels, have a tendency to readily deteriorate polyacetal resins.
Further, while automobile components such as fuel delivery units and the like are covered by enclosures such as the hood or the like, when washing the automobile detergent may adhere due to splashing. In particular, when removing brake dust or the like attached to a wheel, strongly acidic detergents may be used.
Incidentally, for an injection molded article produced from a polyacetal resin, the inner portion of the molded article will have residual stress due to the cooling when injection molding. When this injection molded article contacts a high sulfur-containing fuel or the like, cracks will occur at the locations where the residual stress is large, and this may become the cause of trouble such as fuels leaks and the like. Accordingly, for countries where high sulfur-containing fuels are distributed, a resin material having a high resistance to high sulfur-containing fuels is required as a raw material.
Further, for strongly acidic detergents, there may also be demand for a resin material having a high acid resistance as a required raw material.
As a polyacetal resin composition having a high acid resistance, a polyacetal resin composition comprising (A) 100 parts by mass of a polyacetal resin; (B) 0.1 to 3.0 parts by mass of a hindered phenolic antioxidant; (C) 0.001 to 3.0 parts by mass of a nitrogen-containing compound; (D) 0.1 to 3.0 parts by mass of a fatty acid calcium salt; and (E) 0.1 to 3.0 parts by mass of a lubricant has been proposed (refer to Patent Document 1).    Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2010-031200